Effect of nano ZrO2 on grain growth during sintering of CuAlNi nanostructure

Sintering is one of the main approaches for producing bulk nanostructure materials from powder. It is difficult to maintain the nanostructure during sintering because the high surface to volume ratio and energy accumulated on the grain boundaries increase the driving force of grain growth. This article aims to investigate the effect of nano ZrO2 on grain growth of CuAlNi nanostructure as grain boundary locks. In order to prepare the CuAlNi nanostructure powder, the elemental powders with 0 and 2.5%wt. additive nano ZrO2 was milled for 10h using high energy planetary ball mill. The achieved powder was sintered by hot press at 400 and 600°C at a pressure of 300 MPa for 1 and 2. The X-ray Diffraction (XRD) result of milled powder revealed that the grain size before the sintering was 26 and 15nm for sample without/with additive nano ZrO2, respectively. After sintering, grain growth in the sample without ZrO2 was ten times higher than the sample containing ZrO2. The value of activation energy for grain growth in sample without/with additive nano ZrO2 (90 and 120 kJ/mol), obtained from different scan rate Differential scanning calorimetry (DSC) experiments, is consistent with the above observation. The Field Emission Scanning Electron Microscope (FESEM) image showed pinning of grain boundaries by nano ZrO2 precipitates. The microstructure of sample without ZrO2 had mainly transformed from the nanostructure to the microstructure while the nanostructure of sample containing ZrO2 was maintained by nano ZrO2 particles.